Field of Invention
The present application pertains to the information exchange between the base stations and the radio access network controllers of software-defined wireless broadband communication systems where network slices may be created, altered or revoked programmatically.
Discussion of Related Art
This invention is concerned with the communication method between a control agent and programmable base stations in the radio access network to enable virtualization in the network.
In both second and third generation cellular networks, controllers control base stations. In second generation networks, this controller was called the Base Station Controller (BSC) and was responsible for controlling the channel (time-slot) allocation implemented by the base stations, handovers across the base stations and location tracking of the mobiles in the network. In third generation networks, the controller was renamed as the Radio Network Controller (RNC) and similar to the BSC, it was responsible for radio resource control, channel allocation, power control, handover control, ciphering as well as segmentation and reassembly of the data traffic. Both controllers also act as mobility anchors for the flowing traffic. Besides the standards specifications, there have been a fair number of prior art in architecting systems involving B SCs and RNCs.
U.S. Pat. No. 5,533,028 B2 discusses a BSC in which the guard fields in the TDM-based data flows between itself and the base stations, it controls is reduced to make room for control and signaling information. U.S. Patent Publication 2003/0063582 A1 discusses a BSC that also serves as a gateway to an external packet data network and as such directly transfers flows between this network and the base stations.
U.S. Pat. No. 7,983,712 B2 discusses a centralized RNC architecture to simplify the switching of user data traffic throughout the radio access network. U.S. Patent Publication 2014/0368306 A1 discusses a system where the data communications between the RNC and the base stations use a fixed-length data size or a variable-length data size. The RNC transmits information indicating which packet size option to be used.
U.S. Pat. No. 8,027,676 B2 presents a RNC system that includes a connection setup request transmitter configured to transmit a request to set up the connection to the mobile station located in the specific cell; and a judger configured to judge whether or not to acquire information from the mobile station located in the specific cell. In the system of the invention, the connection setup request transmitter is configured to transmit the connection setup request to the mobile station only when the judger deems necessary to acquire information from the mobile station.
Starting with the fourth-generation cellular network, also known as LTE, the radio network/base station controller has disappeared in the cellular network architecture. Instead, the functionalities of this controller have been moved to the base stations. In other words, the radio resource control, channel allocation, power control, handover control, ciphering and segmentation and reassembly of user data traffic functions are all conducted in a distributed fashion within each base station in LTE.
This invention is intended for fourth generation cellular systems and beyond. In the system of the present invention, a RAN controller is introduced into the network. However, the function of this controller is very different than a BSC or RNC. First, in the network of the invention, the control functionalities of radio resource control, channel allocation, power control, handover control, ciphering and segmentation and reassembly of user data traffic functions still reside on the individual base stations. However, the system of the invention allows for the establishment, modification, and removal of virtual radio access networks, described as RAN slices, programmatically. It is this functionality that the RAN controller of the present invention oversees. The concept of virtualization may be described as a methodology that enables an underlying resource to be shared across multiple consumers, while providing each consumer with the illusion that it owns the entire resource. In wireless systems, specific applications and design goals lead to different virtualization methodologies. We can broadly categorize the concept of wireless virtualization into the following distinct perspectives: wireless network-level virtualization, device-level virtualization, flow-level virtualization, protocol-level virtualization, wireless resources-level virtualization. Most of the previous work on wireless virtualization focuses on a subset of these perspectives.
Wireless Network-Level Virtualization focuses on enabling multiple, isolated logical wireless networks, potentially each operated by a different mobile virtual network operator (MVNO), over a shared physical wireless network infrastructure. There may be different levels of network virtualization for a MVNO. The MVNO may have no infrastructure of its own and may be leasing all aspects of the cellular network from a mobile network operator (MNO) who owns the network infrastructure. Alternatively, the MVNO may own a portion of the network infrastructure, such as network services or even the entire core network, and lease only the access network from a MNO. 3GPP has defined an interoperability requirements document for cellular network-level virtualization for MVNOs. Wireless network-level virtualization may also be employed by a single network operator in order to define various logical networks within its coverage for various purposes.
Device-Level Virtualization focuses on decoupling a portion of the base station equipment from the rest so that the decoupled portion may be realized on commodity hardware in the cloud as a common resource to be shared across a group of base stations. This architecture is commonly referred to as Cloud-RAN in the literature. A typical base station is a distributed architecture composed of the baseband unit (BBU) and remote radio unit (RRU) parts. The BBU is placed in the equipment room and connected to the RRH via optical fiber. The Cloud-RAN architecture typically virtualizes the baseband unit (BBU) functionality in full and realizes them in a centralized pool in the cloud on high-performance programmable processors and real-time virtualization technology. The typical base stations are reduced to simple RRU units with antennas in this case. The U.S. Patent Publication 2014/027792 A1 discusses a Cloud-RAN system and presents a resource scheduling method for the RRU to access the BBU realizations in the cloud.
Flow-Level Virtualization focuses on providing isolation, scheduling, management and service differentiation for both downlink and uplink traffic flows from other flows in a manner similar to how OpenFlow enables flow differentiation for software-defined networks (SDNs). One way of realizing flow-level virtualization is using an overlay filter and software switch module. This method, as described in U.S. Patent Publication 2012/0002620 A1, does not require any modifications to the underlying base station. The patent application defines a group of select flows as a slice, and describes a so-called slice scheduler that is realized outside the base stations. The slice scheduler decides which of the flows should enter the base station and ensures that packets of flows from only the desired slice enter the base station at a given time. The base station then processes these flows in a typical manner by using a flow-level scheduler. Alternatively, flow-level virtualization could also be integrated into the base station protocol stack so that the slice scheduler is implemented within the stack, just before the flow scheduler. The U.S. Pat. No. 8,873,482 B2 discusses a flow-level virtualization for a base station where the uplink and downlink flows are grouped into base station slices. Each slice requests to reserve a portion of the base station resources and is given a normalized weight that reflects this request. The slice scheduler, which is implemented inside the base station, selects which slice to service at a given time, based on the slice weights. For that time, that slice completely controls the base station. It then utilizes a flow scheduler to schedule which flows to service from that slice. The invention disclosed in the patent allows for each slice to have its own flow scheduling function.
Protocol-Level Virtualization focuses on the isolation, customization, and management of multiple protocol instances on one base station equipment. The resource to be virtualized depends on which aspect of the protocol stack is considered. For a MAC-layer virtualization, for example, the scheduling operation may be virtualized. In this case, the base station protocol stack is implemented in such a way that multiple instances of the scheduler may run on it. U.S. Pat. Nos. 8,700,047 B2 and 8,351,948 B2 define flow management functions that contain the operations of virtual time tagging of packets, scheduler operations and model specification operations that specify the relative weights of the flows, and discuss a method to dynamically change the flow management function, and thus the scheduler operation in a base station. Similarly, the U.S. Pat. No. 8,923,239 B2 discusses a base station that dynamically selects a scheduling operation based on a received model specification. Here, the model specification includes a weight distribution, modulation and coding scheme, packet loss value, and minimum and maximum rates of a flow. For a PHY-layer virtualization, on the other hand, the modulation, coding, and other signal processing modules that are implemented on a hardware DSP may be virtualized by defining a DSP sharing scheme for the multiple PHY instances. It is also possible to define a full protocol stack virtualization so that multiple different protocol stacks may operate on the same base station equipment. This is possible using a programmable software-defined radio (SDR) architecture. The SDR allows for a base station to support multiple radio access technologies using the same hardware components.
Wireless Resources-Level Virtualization focuses on the abstraction and dynamic allocation of the wireless radio resources, which are typically defined as a subset of the space defined by the frequency, time, code, power and antenna dimensions. The specific definition of the wireless resources is standard dependent. For example, in LTE, a wireless resource is commonly referred to as a resource block (RB) defined in the frequency-time space. Wireless resources-level virtualization provides the lowest level of slicing possible. There are multiple possible uses for wireless resources-level virtualization. It may be used in a cellular network to reduce the inter-base station interference. For example, U.S. Pat. Nos. 8,660,071 B2 and 8,831,522 B2 present similar distributed dynamic resource partitioning techniques among neighboring base stations so that the potential interference one base station causes to its neighbors is as small as possible. Similarly, the U.S. Patent Publication 2014/0045513 A1 discusses a scenario where multiple operators share wireless resources and a central management server oversees resource partitioning. The resources are dynamically partitioned amongst the operators in different parts of the network via resource ratio change messages sent by the management server. The wireless resources-level virtualization may also be used to satisfy quality-of-service (QoS) requirements of different flows. For example, LTE uses semi-persistent scheduling for voice flows where a specific RB is reserved for the voice call for the entirety of the call. U.S. Pat. No. 8,681,729 B2 discusses reserving specific RBs to multiple flows for a certain duration of time, described by a message. In the case where same RBs are reserved for multiple flows, the system employs a multiplexing technique for the flows to share the common RBs. Alternatively; the wireless resources-level virtualization may be used to allow for multiple instances of the protocol stack to operate on the base station at the same time. If no wireless-level virtualization is present when full protocol stack virtualization is employed, then the architecture remains merely a programmable hardware, where dynamically one can alter the active protocol stack in use as is described in the SDR. However, when both levels of virtualization are present, it is indeed possible for multiple instances of the protocol stack to run in parallel on the base station.
In a system architecture, it is possible to have multiple levels of wireless virtualization at the same time. For example, the U.S. Pat. No. 8,874,125 B2 discusses a wireless system with multiple entities (MNO and MVNOs) that utilizes a virtualization architecture that includes joint wireless network-layer virtualization, flow-level virtualization and partial protocol-layer virtualization. The disclosed system estimates resource requirements of the entities for each base station based on feedback from all base stations, computes the corresponding resource allocations amongst the entities and then enforces flow-level virtualization on each base station using the method of U.S. Pat. No. 8,700,047 B2.
The invention discussed herein proposes a novel system that allows for communication between a RAN controller and a number of base stations to programmatically radio access network virtualization. The framework of the present invention includes joint wireless network-layer virtualization, flow-level virtualization, protocol-layer virtualization and wireless resources-level virtualization using a profile definition. The profile specifies how the network of base stations are virtualized, how the flows within each of these virtual networks are virtualized, and specifies the protocol virtualization for the individual flows as well as the wireless-resources virtualization for them. The invention discusses a system where controllers communicate with base stations to set-up, modify, terminate as well as control the dynamic RAN slices.
Embodiments of the present invention are an improvement over prior art systems and methods.